First constraints on light sterile neutrino oscillations from combined appearance and disappearance searches with the MicroBooNE detector P. Abratenko34D. Andrade Aldana14J. Anthony4L. Arellano19J. Asaadi33A. Ashkenazi31

2025-05-06 0 0 654KB 15 页 10玖币

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First constraints on light sterile neutrino oscillations from combined appearance and

disappearance searches with the MicroBooNE detector

P. Abratenko,34 D. Andrade Aldana,14 J. Anthony,4L. Arellano,19 J. Asaadi,33 A. Ashkenazi,31

S. Balasubramanian,11 B. Baller,11 G. Barr,24 J. Barrow,20, 31 V. Basque,11 L. Bathe-Peters,13

O. Benevides Rodrigues,30 S. Berkman,11 A. Bhanderi,19 M. Bhattacharya,11 M. Bishai,2A. Blake,16 B. Bogart,21

T. Bolton,15 J. Y. Book,13 L. Camilleri,9D. Caratelli,3I. Caro Terrazas,8F. Cavanna,11 G. Cerati,11 Y. Chen,27

J. M. Conrad,20 M. Convery,27 L. Cooper-Troendle,37 J. I. Crespo-Anad´on,5M. Del Tutto,11 S. R. Dennis,4

P. Detje,4A. Devitt,16 R. Diurba,1R. Dorrill,14 K. Duﬀy,24 S. Dytman,25 B. Eberly,29 A. Ereditato,1J. J. Evans,19

R. Fine,17 O. G. Finnerud,19 W. Foreman,14 B. T. Fleming,37 N. Foppiani,13 D. Franco,37 A. P. Furmanski,22

D. Garcia-Gamez,12 S. Gardiner,11 G. Ge,9S. Gollapinni,32, 17 O. Goodwin,19 E. Gramellini,11 P. Green,19

H. Greenlee,11 W. Gu,2R. Guenette,19 P. Guzowski,19 L. Hagaman,37 O. Hen,20 R. Hicks,17 C. Hilgenberg,22

G. A. Horton-Smith,15 B. Irwin,22 R. Itay,27 C. James,11 X. Ji,2L. Jiang,35 J. H. Jo,37 R. A. Johnson,7Y.-J. Jwa,9

D. Kalra,9N. Kamp,20 G. Karagiorgi,9W. Ketchum,11 M. Kirby,11 T. Kobilarcik,11 I. Kreslo,1M. B. Leibovitch,3

I. Lepetic,26 J.-Y. Li,10 K. Li,37 Y. Li,2K. Lin,26 B. R. Littlejohn,14 W. C. Louis,17 X. Luo,3K. Manivannan,30

C. Mariani,35 D. Marsden,19 J. Marshall,36 N. Martinez,15 D. A. Martinez Caicedo,28 K. Mason,34 A. Mastbaum,26

N. McConkey,19 V. Meddage,15 K. Miller,6J. Mills,34 A. Mogan,8T. Mohayai,11 M. Mooney,8A. F. Moor,4

C. D. Moore,11 L. Mora Lepin,19 J. Mousseau,21 S. Mulleriababu,1D. Naples,25 A. Navrer-Agasson,19 N. Nayak,2

M. Nebot-Guinot,10 J. Nowak,16 M. Nunes,30 N. Oza,17 O. Palamara,11 N. Pallat,22 V. Paolone,25

A. Papadopoulou,20 V. Papavassiliou,23 H. B. Parkinson,10 S. F. Pate,23 N. Patel,16 Z. Pavlovic,11 E. Piasetzky,31

I. D. Ponce-Pinto,37 I. Pophale,16 S. Prince,13 X. Qian,2J. L. Raaf,11 V. Radeka,2M. Reggiani-Guzzo,19

L. Ren,23 L. Rochester,27 J. Rodriguez Rondon,28 M. Rosenberg,34 M. Ross-Lonergan,17 C. Rudolf von Rohr,1

G. Scanavini,37 D. W. Schmitz,6A. Schukraft,11 W. Seligman,9M. H. Shaevitz,9R. Sharankova,11 J. Shi,4

A. Smith,4E. L. Snider,11 M. Soderberg,30 S. S¨oldner-Rembold,19 J. Spitz,21 M. Stancari,11 J. St. John,11

T. Strauss,11 S. Sword-Fehlberg,23 A. M. Szelc,10 W. Tang,32 N. Taniuchi,4K. Terao,27 C. Thorpe,16 D. Torbunov,2

D. Totani,3M. Toups,11 Y.-T. Tsai,27 J. Tyler,15 M. A. Uchida,4T. Usher,27 B. Viren,2M. Weber,1H. Wei,18

A. J. White,37 Z. Williams,33 S. Wolbers,11 T. Wongjirad,34 M. Wospakrik,11 K. Wresilo,4N. Wright,20

W. Wu,11 E. Yandel,3T. Yang,11 L. E. Yates,11 H. W. Yu,2G. P. Zeller,11 J. Zennamo,11 and C. Zhang2

(The MicroBooNE Collaboration)∗

1Universit¨at Bern, Bern CH-3012, Switzerland

2Brookhaven National Laboratory (BNL), Upton, NY, 11973, USA

3University of California, Santa Barbara, CA, 93106, USA

4University of Cambridge, Cambridge CB3 0HE, United Kingdom

5Centro de Investigaciones Energ´eticas, Medioambientales y Tecnol´ogicas (CIEMAT), Madrid E-28040, Spain

6University of Chicago, Chicago, IL, 60637, USA

7University of Cincinnati, Cincinnati, OH, 45221, USA

8Colorado State University, Fort Collins, CO, 80523, USA

9Columbia University, New York, NY, 10027, USA

10University of Edinburgh, Edinburgh EH9 3FD, United Kingdom

11Fermi National Accelerator Laboratory (FNAL), Batavia, IL 60510, USA

12Universidad de Granada, Granada E-18071, Spain

13Harvard University, Cambridge, MA 02138, USA

14Illinois Institute of Technology (IIT), Chicago, IL 60616, USA

15Kansas State University (KSU), Manhattan, KS, 66506, USA

16Lancaster University, Lancaster LA1 4YW, United Kingdom

17Los Alamos National Laboratory (LANL), Los Alamos, NM, 87545, USA

18Louisiana State University, Baton Rouge, LA, 70803, USA

19The University of Manchester, Manchester M13 9PL, United Kingdom

20Massachusetts Institute of Technology (MIT), Cambridge, MA, 02139, USA

21University of Michigan, Ann Arbor, MI, 48109, USA

22University of Minnesota, Minneapolis, MN, 55455, USA

23New Mexico State University (NMSU), Las Cruces, NM, 88003, USA

24University of Oxford, Oxford OX1 3RH, United Kingdom

25University of Pittsburgh, Pittsburgh, PA, 15260, USA

26Rutgers University, Piscataway, NJ, 08854, USA

27SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA

arXiv:2210.10216v3 [hep-ex] 6 Dec 2022

28South Dakota School of Mines and Technology (SDSMT), Rapid City, SD, 57701, USA

29University of Southern Maine, Portland, ME, 04104, USA

30Syracuse University, Syracuse, NY, 13244, USA

31Tel Aviv University, Tel Aviv, Israel, 69978

32University of Tennessee, Knoxville, TN, 37996, USA

33University of Texas, Arlington, TX, 76019, USA

34Tufts University, Medford, MA, 02155, USA

35Center for Neutrino Physics, Virginia Tech, Blacksburg, VA, 24061, USA

36University of Warwick, Coventry CV4 7AL, United Kingdom

37Wright Laboratory, Department of Physics, Yale University, New Haven, CT, 06520, USA

(Dated: December 8, 2022)

We present a search for eV-scale sterile neutrino oscillations in the MicroBooNE liquid argon

detector, simultaneously considering all possible appearance and disappearance eﬀects within the

3 + 1 active-to-sterile neutrino oscillation framework. We analyze the neutrino candidate events for

the recent measurements of charged-current νeand νµinteractions in the MicroBooNE detector,

using data corresponding to an exposure of 6.37×1020 protons on target from the Fermilab booster

neutrino beam. We observe no evidence of light sterile neutrino oscillations and derive exclusion

contours at the 95% conﬁdence level in the plane of the mass-squared splitting ∆m2

41 and the sterile

neutrino mixing angles θµe and θee , excluding part of the parameter space allowed by experimental

anomalies. Cancellation of νeappearance and νedisappearance eﬀects due to the full 3+1 treatment

of the analysis leads to a degeneracy when determining the oscillation parameters, which is discussed

in this paper and will be addressed by future analyses.

The discoveries of solar [1] and atmospheric neutrino

oscillations [2] have motivated a broad experimental pro-

gram dedicated to studying neutrino mixing. While most

measurements [3–13] are consistent with three-ﬂavor (3ν)

neutrino oscillations as described by the Pontecorvo-

Maki-Nakagawa-Sakata (PMNS) formalism [14–16], sev-

eral experimental anomalies [17–27] can possibly be ex-

plained by a hypothetical sterile neutrino with a mass at

the eV scale [15, 28]. The SAGE [17] and GALLEX [18]

experiments, and more recently, the BEST [19, 20]

experiment, have observed lower than expected νerates

from radioactive sources, which is known as the gallium

anomaly. Reactor neutrino experiments have measured

lower ¯νerates [21] than the expectation based on reactor

anti-neutrino ﬂux calculations [22, 23]. This observation

is referred to as the reactor anomaly. An oscillation

signal in the reactor ¯νeenergy spectrum over distances

of a few meters was reported by the Neutrino-4 [24]

collaboration. In addition to these observed (–)

νedeﬁcits,

excesses of (–)

νe-like events were also observed in some (–)

νµ

dominated accelerator neutrino experiments. The LSND

collaboration [25] observed an anomalous excess of ¯νe-

like events, and the MiniBooNE collaboration [26, 27]

observed an excess of low-energy electron-like events.

These anomalies are in strong tension with other

experimental results within the 3(active) + 1(sterile) os-

cillation framework as seen in a global ﬁt of the data [29].

In addition, recent experimental measurements [30, 31]

and improvements of the reactor anti-neutrino ﬂux

calculation [32, 33] lead to a plausible resolution of

the reactor anti-neutrino anomaly. The Neutrino-4

∗microboone info@fnal.gov

anomaly is largely excluded by the results from other

very short baseline reactor neutrino experiments, for

example, PROSPECT [34], STEREO [35], DANSS [36],

NEOS [37], although it is consistent with the gallium

anomaly.

The MicroBooNE collaboration has recently reported

a ﬁrst set of searches related to the MiniBooNE low-

energy excess, targeting multiple ﬁnal-state topologies

of the charged-current (CC) νeinteractions [38–41]

and the neutral-current (NC) ∆ resonance decay that

produces a single photon in the ﬁnal state [42]. The

MicroBooNE detector [43] has a similar location and is

exposed to the same booster neutrino beam (BNB) [44]

as the MiniBooNE detector. Utilizing the liquid argon

time projection chamber (LArTPC) technology that

can provide good e/γ separation, MicroBooNE has

achieved high-performance νeselections and observes

no evidence of a νeexcess [38–41]. These results

disfavor the hypothesis that the MiniBooNE low-energy

excess originates solely from an excess of νeinteractions.

Instead, one or more additional mechanisms [45–52] are

required to explain the MiniBooNE observations.

A light sterile neutrino would profoundly impact

fundamental physics. In addition to testing models that

may explain both the MicroBooNE and MiniBooNE low-

energy νeobservations, interpreting the MicroBooNE

νeresults in the context of a sterile neutrino can

provide valuable statements beyond the conclusions

already reached by the current analyses, and examine the

remaining experimental anomalies that may be explained

by a sterile neutrino. Recent phenomenological studies

have examined the MicroBooNE νeresults in the context

of a sterile neutrino hypothesis. One study [53] considers

aνedisappearance-only hypothesis, while another [54]

considers the full 3 + 1 oscillation eﬀect.

In this Letter, we present a new analysis testing the

sterile neutrino hypothesis in a full 3 + 1 oscillation

framework with detailed event-level information. We

use the data set from the MicroBooNE inclusive νe

CC measurement [41], and compare the results to

the parameter space allowed by the LSND, gallium

(including BEST), and Neutrino-4 anomalies. We

simultaneously consider short-baseline sterile-neutrino-

induced νeappearance and νedisappearance. This

treatment can lead to cancellations that result in a

degeneracy when determining the oscillation parameters,

which we will introduce in more detail in this paper.

The MicroBooNE detector [43] is a 10.4 m long, 2.6 m

wide, and 2.3 m tall LArTPC, located on-axis of the

BNB at Fermilab. It consists of about 85 metric tons

of liquid argon in the TPC active volume for ionization

charge detection along with an array of photomultiplier

tubes [55] for scintillation light detection. It sits at a

distance of 468.5 m from the target of the BNB, which

uses protons with a kinetic energy of 8 GeV impinging on

the target, producing secondary hadrons. The hadrons

are mostly pions or kaons that decay in ﬂight, producing

a neutrino beam through their decay. The MicroBooNE

BNB data set was collected entirely in neutrino mode

and consists of a very pure νµbeam with a small ¯νµ

contamination and a νecontamination of <1%.

We perform a full 3 + 1 (4ν) neutrino oscillation

analysis, capitalizing on the seven channels of νe

and νµselections and their statistical and systematic

uncertainties from the MicroBooNE inclusive νelow-

energy excess search [41]. The analysis uses the BNB

Runs 1–3 data set with an exposure of 6.369×1020

protons on target (POT). In addition to the standard

Monte Carlo (MC) samples for intrinsic νeand νµevents

in the BNB, a dedicated νµ→νeoscillation sample

was generated to appropriately take into account the

ﬂux and cross-section systematic uncertainties related to

the νeappearance events. The seven channels comprise

fully contained (FC) and partially contained (PC) νeCC

processes, FC and PC νµCC processes without ﬁnal-

state π0mesons, FC and PC νµCC processes with

ﬁnal-state π0mesons, and a NC channel with ﬁnal-

state π0mesons. The fully contained events are deﬁned

as those that have all reconstructed TPC activity (i.e.,

charge depositions) within a ﬁducial volume 3 cm from

the TPC boundaries. Because there are νµand νe

components in the BNB ﬂux, the νeappearance (from

νµ), νedisappearance, and νµdisappearance oscillation

eﬀects in the 3 + 1 framework are simultaneously applied

to the predicted signal and background events in all

seven channels in the oscillation ﬁt. The νµappearance

eﬀect is neglected because of the very low fraction of

intrinsic νein the BNB ﬂux. This strategy takes full

advantage of the statistics of the selected νeand νµ

events in the FC and PC channels, and at the same time

maintains the capability to apply data constraints across

channels through a joint ﬁt to the seven channels, thereby

reducing the systematic uncertainty in the oscillation

analysis. The neutrino energy reconstruction primarily

follows a calorimetric method with an energy resolution

of approximately 10–15% and a bias of 5–10% for CC

events [41]. In the reconstruction of NC events, we

use this method to estimate the energy transfer with

an invisible outgoing neutrino. The reconstruction of

visible energy for the NC events in this analysis has a

similar bias and energy resolution to the neutrino energy

reconstruction of CC events.

We use an extended 4 ×4 unitary PMNS matrix

(U) to describe the 3 + 1 neutrino mixing between the

ﬂavor and mass eigenstates. Following the common

parameterization [29, 56], the elements of Urelevant to

this Letter can be expressed as

|Ue4|2= sin2θ14,

|Uµ4|2= cos2θ14 sin2θ24,(1)

|Us4|2= cos2θ14 cos2θ24 cos2θ34,

where sdenotes the sterile neutrino ﬂavor. Given the

energy range of the neutrino ﬂux at MicroBooNE, in

the parameter space with ∆m2

41  |∆m2

31|, the short-

baseline oscillation probability from α-ﬂavor to β-ﬂavor

neutrinos in vacuum approximates to

Pνα→νβ=δαβ + (−1)δαβ sin22θαβ sin2∆41,(2)

where δαβ is the Kronecker delta,

∆41 ≡∆m2

41L

4E= 1.267 ∆m2

eV2MeV

EL

m,(3)

and

sin22θαβ = 4|Uα4|2|δαβ − |Uβ4|2|.(4)

We deﬁne θαβ as the eﬀective mixing angles, which can

be expressed as

sin22θee = sin22θ14,

sin22θµe = sin22θ14 sin2θ24,

sin22θµµ = 4cos2θ14sin2θ24(1 −cos2θ14sin2θ24),(5)

sin22θes = sin22θ14 cos2θ24 cos2θ34,

sin22θµs = cos4θ14 sin22θ24 cos2θ34.

Ignoring the oscillation eﬀect in the negligible neutrino

background outside of the detector cryostat, for the other

CC and NC signal or background events in all seven

channels, we use sin22θee and sin22θµe to predict the

νeCC energy spectrum, sin22θµµ to predict the νµCC

energy spectrum, and sin22θes and sin22θµs to predict

the NC energy spectrum. We ﬁx θ34 to 0 (cos2θ34 = 1)

since it has a negligible impact in this analysis given

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FirstconstraintsonlightsterileneutrinooscillationsfromcombinedappearanceanddisappearancesearcheswiththeMicroBooNEdetectorP.Abratenko,34D.AndradeAldana,14J.Anthony,4L.Arellano,19J.Asaadi,33A.Ashkenazi,31S.Balasubramanian,11B.Baller,11G.Barr,24J.Barrow,20,31V.Basque,11L.Bathe-Peters,13O.BenevidesRodri...

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First constraints on light sterile neutrino oscillations from combined appearance and disappearance searches with the MicroBooNE detector P. Abratenko34D. Andrade Aldana14J. Anthony4L. Arellano19J. Asaadi33A. Ashkenazi31.pdf

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First constraints on light sterile neutrino oscillations from combined appearance and disappearance searches with the MicroBooNE detector P. Abratenko34D. Andrade Aldana14J. Anthony4L. Arellano19J. Asaadi33A. Ashkenazi31

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